The present invention relates to a heparin-binding protein functionalized by covalently bonding thereto a sugar chain, a method for producing the protein and a pharmaceutical composition containing the protein.
It has been known that heparin-binding proteins, among all, those proteins classified into the fibroblast growth factor (hereinafter, referred to as “FGF”) family and fibroblast growth factor homologous factors strongly bind to heparin and heparan sulfate (sulfated polysaccharides) by a non-covalent bond. It has been also known that when a heparin-binding protein such as fibroblast growth factor is mixed with a sulfated polysaccharide such as heparin, the biological activity and physical properties of the heparin-binding protein are altered to change its function; sometimes, such a heparin-binding protein may acquire higher function. However, even if a sulfated polysaccharide was mixed with, the expected functionalization of the protein has been limited. Besides, when such a mixture is used as a pharmaceutical composition, unfavorable physiological activity attributable to a free sulfated polysaccharide has caused a problem. To date, there has been reported no protein in which a heparin-binding protein is joined with a sulfated polysaccharide by a covalent bond for the purpose of functionalization of the heparin-binding protein.
In addition, it has never been known to date that artificial addition of an asparagine-linked sugar chain (hereinafter, referred to as an “N-linked sugar chain”) or serine/threonine-linked sugar chain (hereinafter, referred to as an “O-linked sugar chain”) to a heparin-binding protein, particularly a protein of the FGF family or a fibroblast growth factor homologous factor, by a covalent bond can functionalize the protein. Furthermore, the general effect which an N-linked sugar chain or O-linked sugar chain could give has not been known. Exceptionally, with respect to FGF-6, the role of the N-linked sugar chain it naturally has was suggested in an in vitro translation system, but has not been proved directly. To date, there has been reported no example of joining a heparin-binding protein with an N-linked or O-linked sugar chain by a covalent bond for the purpose of functionalizing the heparin-binding protein.
It is an object of the present invention to improve the function of heparin-binding proteins. It is another object of the invention to establish a heparin-binding protein to which a sugar chain is covalently bonded and a method for producing the protein. It is still another object of the invention to provide a pharmaceutical composition containing the above protein.